Foam-plastic skiving machine



H. ,KERNEN FOAM-PLASTIC SKIVING MACHINE Jan. 28, 1958 4 Sheets-Sheet 1Filed Oct. 4. 1954 &

Jan. 28g 1958' H. KERNEN 2,321,254

FOAM-PLASTIC SKIVING MACHINE Filed Oct. 4, 1954 4 Sheets-Sheet 2 Jan.28, 1958 H. KERNEN FOAM-PLASTIC SKIVING MACHINE 4 Sheets-Sheet 3 FiledOct. 4, 1954 H.KERNEN FOAM-PLASTIC SKIVING MACHINE a3am. 28, 1953 4Sheets-Sheet Filed Oct. 4, 1954 if 3 2 33 a4 2334233132 i Ll UnitedStates Patent FOAloi-PLASTIC SKIVING MACHINE I-Ians Kernen, Bern,Switzerland Application October 4, 1954, Serial No. 460,156

Claims priority, application Switzerland October 10, 1953 9 Claims. (Cl.164-75) In the arts and industry there is a growing demand forfoamed-plastic foils. Foamed plastic is rather expensive and is suppliedby the manufacturers only in sheets of at least inch thickness andmostly in thicknessesof one inch and more. So far it has beenpractically impossible to skive or cut up such sheets into foils, and inparticular into foils having a smooth surface.

The main object of my present invention istoremedy such disadvantage.According to the method disclosed by my present invention, a skiver orknife having a serrated cutting edge is moved through the sheet andsubjected to longitudinal oscillations with such frequency that thefoamed plastic to be cut cannot resonate.

In the skiving machine disclosed herein, the longitudinally oscillatableskiver is a stretched spring-steel band: of

which one longitudinal edge forms the cutting edge, being;

ground towards the underside in serrated and pointed manner.

One form of my present invention is shown, by way of example, in theaccompanying drawing which also serves to illustrate the methoddisclosed by the invention. In the drawings:

Fig. 1 shows the machine in elevation,

Fig. 2 is a top plan view thereof,

Fig. 3 is a cross-section on the line III--III of Fig. 2,

Fig. 4 is a horizontal section on the line IV--IV of Fig. 3, and shows,in an enlarged scale, details of the bearing and driving arrangement ofthe knife, and

Figs. 5 to 7 are cross-sections on the lines VV, VI-VI and VII-VII ofFig. 4 respectively.

As shown in Fig. l, the skiving machine comprises a stand which in themain is composed of corner posts 1, a lower frame 2, side sheets 3 and4, two horizontal and parallel top box-girders 5, and bracing tubes 6interconnecting the latter. To the girders 5 is secured a plate 7, e. g.by welding, which serves a table. The foamedplastic sheet 8 to be cutinto foils, either is secured to said table by adhesive means or simplylaid thereon.

As shown in Fig. 3, a screw spindle 10 is rotatably but axiallyimmovably mounted in two bearings 9 disposed on transverse members ofthe stand outside of the side sheets 4. Said spindle coacts with a nut11 which by means of lateral forked wings 12 is guided on two rails 13secured to the sheets 4. To nut 11 are secured the ends of two steelcables 14 trained over idling discs 15 mounted on the stand. An electricmotor 17 mounted on frame 2 rotates spindle 10 through a belt drive 16and, thus, moves nut 11 and the two cables 14 in one or the other sense.Outside the girders 5 and parallel thereto are arranged guide rods 18 ofwhich the end faces through gussets 19 are connected to said girders. Onrod 18 is movably mounted a sleeve 20 to which is welded a horizontalplate 21. The opposite ends of the cables are fixed to the sleeves 20,as shown in Figs. 2 and 3. Thus, when the nut is moved, the sleeves 20and the parts carried thereby are moved. For example, when the nut 11,as shown in Figs. 1 and 2, is moved to the left, the sleeves 20 and theparts carried thereby are moved to the right. In a ring 22 welded to thelatter is rigidly mounted a guide column 23. The two columns 23 arerigidly interconnected ontop througha horizontal transverse member 24 inwhich two screw spindles 25 are mounted rotatably but axially immovably.The spindles 25 through two bevel gears 26 are drivably connected to ashaft 27 which is rotatable in bearings 28 fixed to member 24 and on oneend of which is provided a graduated disc 29 and a crank 30. Each of thespindles 25 coacts with a threaded bush 31 rigidly inserted in a holder32. The latter is screwed to a lateral lug 33 of a sleeve 34 which is'longitudinally movable on the asso ciated column 23, as shown in- Figs.3 and 4.

As shown in Figs. 3 and 4, lugs 36 of a. knife beam 71 are insertedbetween the lugs 33 and. secured thereto by screws 35. Lugs 33 and 36together form arigid carrier for two similar two-arm oscillating levers37 and 37a of which the bearings are designated by 38. Each of' saidlevers comprises a piece of pipe 39' welded to one of the lugs 33, asliding bush 40 inserted in pipe 39, a bearingpin 41 welded to saidlever, a screw 42 mounted and secured in pin 41', and a disc 43supported on the upper end face of bush 40 for taking up the smallaxialforces. The front forked ends 44' of the levers 37, 37a areprovided with ahoriz-ontal slot 45 in which is inserted one or the otherend of. a skiver or knife blade 46-, the latter being mounted on ahardened screw 47. The rear ends of the two oscillating levers areinterconnected through astretching device comprising a threaded member48', a threaded wire-receiving sleeve 49, a stretching wire 50 and amember 51. Lever 37a has a lug 52 to which ispivoted, on a screw 53, abar 54 of an eccentric ring- 55. The latter by means of balls 56' ismounted on the eccentric pin 57 of a shaft 58 which is rotatable in abearing 59 whicfr through parts 60, 61 is fixed to the adjacent sleeve34. Shaft 58 through a belt drive 62 to 64 is connected to an. electricmotor 65 which is screwed down on a plate 66 welded to part 61.

As shown in Figs. 4 and 7, arms 68' are pivotally mounted in bosses 67of the lugs 33. In bores of thelatter are rotatably mounted pins 69 of aloading roller 70 which is parallel to the cutting; edge of knife blade46 and slightly in front of'the latter. Roller 70 serves to pressdownthe plastic sheet 8 ontoa coating 85 oftable 7", which coatingincreases the friction. Roller 70 in an extreme case may be situatedonly slightly lower with respect to knife 46 than shown in the drawing,as the arms 68 then rest on member 36.

Knife 46 is reciprocated at least 800 times per minute by motor 65through the eccentric drive 55, 57 and lever 37a, and is made of aspring-steel band of which the longitudinal edge forming the cuttingedge is serrated and ground sharply towards the underside in a mannersimilar to that of bread knives. The rear longitudinal edge of the knifemoves in a guide formed on knife beam 71 of which the underside 72 isparallel to the knife underside, the spacing not exceeding the knifethickness. Such spacing corresponds to the thickness of a sheet 73 whichat 75 is riveted to another horizontal sheet 74. The rear and topportion of said guide is formed on a solid constructional member 76 oftriangular cross-section. To stepped surfaces at the rear of member 76are brazed the lower and upper sheets 74 and 77 respectively, of abox-like structure to the somewhat thicker sidewall sheets 78 of whichare welded the lugs 36. Said structure at the rear is braced by asheet-iron member 79 of U-shaped cross-section. Fig. 6 further showsthat the knife-beam upperside 80 rises rearwardly from a front edge 81which is spaced from knife-beam upperside 80 by one to two knifethicknesses, first only at a slight slope and then somewhat steeper.

The carriage by the sleeves 20 is guided on the rods 18 which over theirentire length are protected from impurities thr'oughcover plates 82which are secured to the plates 19. For the operation of cutting offfoils fiom the sheet 8 stuck to table 7, the carriage is run back untilthe cutting edge of knife 46 is situated in front of sheet 8 (Figs. Gand 7). Byactuating crank 30, the foil thickness :,is set, whereupon afoil may be cut off when motor 65 is operating.

At the end of the forward and rearward runs of the carriage, motor 17 isreversed or stopped through limit switches 83 (Fig. 3) secured to thestand and through cams 84 secured to the carriage.

Tests have shown that with the machine disclosed, foils of very goodsurface property and minimal thickness of approximately of an inch maybe cut off from foamplastic sheets up to 3% inches thick, provided thatthe frequency of the knife oscillations is sufficiently higher than thefrequency at which the surface of sheet 8 could resonate. A frequency of800 per minute is quite sufficient in most cases. In order to diminishthe foil surface roughness, it is advisable to make the tooth backsomewhat rounded, i. e. to avoid burrs on the ground face of the knifeserrations. The machine shown and described is only an example which inmany details could be varied without leaving the scope of the invention.

What I claim as new and desire to secure by Letters Patent is:

1. A method of cutting off foils from a foam-plastic sheet, comprisingthe steps of supporting the sheet in a flat superposed position on afirm supporting surface, advancing a knife having a serrated cuttingedge longitudinally of the surface and through said sheet and ofsimultaneously subjecting said knife to longitudinal oscillations with'a frequency of such rate that the sheet to be cut cannot resonate;

2. A method as set out in claim 1, in which the frequency of saidlongitudinal oscillations is at least 800 per minute.

3. A method as set out in claim 1, in which the sheet portion situatedin front of the cutting edge is held down by a slight, non-deformingpressure on the surface.

4. A machine for cutting ofi foils from a foam-plastic sheet oomprisinga horizontal supporting table on which the sheet is laid flat, avertically adjustable frame transversely overlying the table, a springsteel cutting knife carried by the frame and positioned transverse ofthe sheet, said knife having a longitudinal cutting edge facing thesheet, means for longitudinally oscillating the knife,

4 guide means in which the opposite longitudinal side edge of. the knifeis guided as the knife is longitudinally oscillated and means for movingthe frame longitudinally of the table to advance the knife through thesheet.

5. A machine as claimed in claim 4, wherein the cutting edge is serratedand sharply ground towards the knife underside.

6. A machine as claimed in claim 4, wherein the guide is carried by theframe and has a slot in which the opposite longitudinal edge of theknife slides, the guide consisting of a knife beam having a flatunderside which is spaced from the underside of-the knife by an amountless than the thickness of the knife. I

7. A machine as claimed in claim 4, wherein the guide is a knife beamwhich has a slot in which the opposite 1ongitudinal edge of the knifeslides, the knife beam having an upper surface which slopes rearwardlyfrom the knife, the front edge of the beam, in which the slot is formed,being a distance of from one to two knife thicknesses above the knife. I

8. A machine as claimed in claim 4, wherein said means forlongitudinally oscillating the knife includes a pair of spaced apart,parallel horizontal arms, disposed transversely of the ends of theknife, means connecting the ends of the knife to one of the ends of thearms, axially adjustable stretching means interconnecting the oppositeends of the arms to stretch the knife, means mounting the arms,intermediate their ends, for pivotable movement 7 about vertical axes,and power means connected to one of the arms for oscillating the arms.

9. A machine as claimed in claim 8, wherein said last means includes adrive motor, an eccentric driven thereby and a link connection betweenthe eccentric and one of the 'arms.

References Cited in the file of this patent UNITED STATES PATENTSAustria Nov. 10, 1932

